// n must be at most 3 below a.length*4
static byte[] intArrayToBytes_littleEndian_flexLength(int[] a, int n) {
  byte[] b = new byte[n];
  for (int i = 0; i < n/4; i++)
    intToBytes_inArray_littleEndian(a[i], b, i*4);
  if (a.length > n/4)
    intToBytes_inArray_littleEndian_partial(a[a.length-1], b, (a.length-1)/4);
  ret b;
}